Is .NET really cross-platform?

The language C itself is cross-platform , because you don’t directly run C code on machines. The C source code is compiled to assembly, and assembly is the platform specific code. The only non cross-platform part are the compilers and the resulting assembly.

Yes, C# is fully cross-platform thanks to . NET Core . . NET Core is a free and open-source, managed computer software framework for Windows, Linux, and macOS operating systems.11 Kas 2011

While originally built to run on Windows, C# was quickly ported to Linux and macOS by the Mono project. Today, C# is open source and runs on the cross-platform . NET Core .

First, . NET Core is cross-platform . It runs on Windows, OS X and multiple distributions of Linux.